1. Field of the Invention
The invention relates to a device for exposure of a peripheral area, in which an unnecessary resist which has been applied to the peripheral area of a film circuit board, such as a TAB strip or the like, is exposed.
2. Description of Related Art
In a liquid crystal substrate, a cellular telephone, a camera, a calculator, an IC card or the like, a film circuit board is used in which an integrated circuit is applied to a polyester film, a polyimide film, or the like with a thickness of roughly 25 microns to 125 microns. FIG. 5(a) shows part of a TAB strip as one of the film circuit boards. The TAB strip TP is a strip workpiece with a width of 35 mm to 70 mm and a length of a few hundred millimeters and which is conventionally wound onto a reel.
A circuit is produced on the TAB strip TP by pressing a conductive foil (for example, a copper foil) to the above described insulating film and by repeating the following processes and the like. Applying a resist, performing an exposure process in which the desired circuit pattern is transferred, developing the resist, and performing etching process in which the unnecessary conductive foil is removed. In the given process, the film circuit board is unwound from a reel, treated and processed, and re-wound onto a reel.
The TAB strip TP (hereinafter also called a strip) is provided on both sides with perforation holes PH (also called sprocket holes) which have the same distance to one another (for example, with a pitch of 4.75 mm) and which are used for positioning and transporting the strip TP in the above described respective process. The strip TP is transported, for example, by rotating rollers having projections which are received into the perforation holes PH. Furthermore, in treatments such as exposure and the like, the strip TP is positioned by inserting pins located at given positions of the device into the perforation holes PH.
When performing the etching process, the unnecessary conductive foil (hereinafter also called copper foil Cu) is removed. If the conductive foil is not sufficiently removed, insulation faults and the like occur, and thus, scrap is formed. Furthermore, there is the disadvantage of a poor appearance.
FIG. 5(b) is a cross sectional view of FIG. 5(a) and illustrates a state in which a resist R has been applied to the copper foil Cu of the TAB strip TP. As was described above, the copper foil Cu is pressed to an insulating film. On the edge of the copper foil (hereinafter also called the peripheral area), the applied resist R projects as a result of surface tension, thereby causing the edge to be thicker than the remaining area.
Conventionally a circuit pattern is formed such that a peripheral area of the copper foil Cu is avoided. The area in which a circuit pattern is formed is shown in FIG. 5 (a) as the xe2x80x9carea in which the pattern is generatedxe2x80x9d. Also, conventionally, the peripheral area of the copper foil Cu is removed in the etching process. However, since the resist R in the peripheral area of the copper foil is thick, a larger exposure amount than in the remaining area (i.e., the area in which the pattern is generated) is needed for complete exposure. In a one-time exposure (i.e., an exposure when the pattern is being generated), the exposure amount is insufficient, whereby upon development in the peripheral area not yet exposed, resist remains and in the etching process the copper foil is not removed.
As shown in FIGS. 6 and 7, Japanese Patent Application JP 2000-187646, U.S. patent application Ser. No. 09/886005 and European Patent Application EP 01114566.1 each disclose a process for exposing the peripheral area in which only the resist in the peripheral area of the copper foil is exposed. FIG. 6 shows a device for exposing a peripheral area viewed from a direction which orthogonally intersects the transport direction of a film circuit board (hereinafter also called xe2x80x9cTAB strip TPxe2x80x9d). In FIG. 7, this device is viewed from a transport direction of a film circuit board. The device for exposure of a peripheral area is located at two points per strip, i.e., on both sides for one strip, and upstream of a device for developing the film circuit board, i.e., in the step before development. The TAB strip TP is continuously transported according to the development speed at 1.0 to 3.0 m/minute. During this transport, the resist is exposed in the peripheral area of the copper foil.
In FIGS. 6 and 7, the TAB strip TP is transported by delivery rollers R1 and R2 on a carrier 3 in a transport direction shown by the arrows in the drawings. An exposure light, such as ultraviolet light UV, for exposing the resist on the TAB strip TP is delivered by a light source part 1 which has a lamp 1a and a condenser mirror 1b through a quartz optical fiber 1c via a mask (not shown) which partially screens the exposure light. A projection lens unit 2 condenses the exposure light on the peripheral area of the copper foil of the TAB strip TP located on the carrier 3. Accordingly, the exposure light irradiation area is formed specifically by the mask and is projected by the projection lens unit 2 on the TAB strip TP. The edge of the copper foil pressed to the TAB strip TP is determined by an optical detector 4 which includes a projection part 4a which transmits a sensor light and a light receiving part 4b. The sensor light which emerges from the projection part 4a is received by the edge part of the copper foil and a gap located in the carrier 3 by the light receiving part 4b. 
The optical detector 4 can be, for example, a parallel light linear sensor with a semiconductor laser. The sensor light emitted by the projection part 4a of the parallel-light linear sensor (i.e., nonexposure light) is laser light and propagates well in a straight line. When projected perpendicular relative to a flat body, the light becomes strip-shaped. The light receiving part 4b can completely receive the light from the projection part 4a at a given distance and furthermore can determine the change in the amount of light received.
The projection part 4a and the light receiving part 4b of the optical detector 4 are installed in a component 6 which, in turn, is installed in a sliding base 5 driven by a drive motor 7 in a direction which orthogonally intersects the transport direction of the TAB strip TP. The projection lens unit 2 is also installed in the sliding base 5. Thus, when the sliding base 5 is moved by the drive motor 7 in the direction of the arrow in FIG. 7, the projection lens unit 2 and the optical detector 4 also move accordingly in the same direction.
In FIG. 7, a controller 8 is provided into which a signal is input with a magnitude which corresponds to the intensity of the light received by the light receiving part 4b of the optical detector 4 (i.e., the amount of light received). The controller 8 drives the drive motor 7, and thus, moves the optical detector 4 and the sliding base 5 such that the above described amount of light received is always constant. Since an exit part (containing the projection lens), which encompasses the projection lens unit 2 and from which the peripheral area exposure light emerges, is installed in the sliding base 5, the position of the irradiation area of the exposure light emitted by the above described exit part is changed by the sliding base 5 moving. In other words, the optical detector 4 moves such that the amount of light received is always constant. The exposure light irradiation area moves to the same degree and in the same direction as the amount of motion of the sensor and its direction of motion in the direction which orthogonally intersects the transport direction of the TAB strip TP.
As shown in FIG. 8, the film circuit board, i.e., the TAB strip TP, is formed by pressing a copper foil onto a film which is an organic compound. Since the copper foil is pressed by application of heat and pressure, an arch may be formed as a result of the different thermal expansion coefficients between the copper foil and the film or for similar reasons, after pressing in the transverse direction of the strip. Furthermore, for a TAB strip TP with perforation holes, a fold may be formed in the strip peripheral area which is provided with perforation holes as a result of expansion and deformation if, in the previous process, the TAB strip is transported by a sprocket roller which engages the perforation holes.
If an arch and/or a fold is formed in the peripheral area of the strip, as shown in FIG. 8, when the resist of this peripheral area is exposed, the position of the strip peripheral area to be exposed relative to the focal position of the exposure light through to the projection lens of the device for exposing a peripheral area deviates in the direction of the optical axis of the emitted exposure light. Thus, the mask edge image projected onto the strip peripheral area becomes blurred, by which the exposure accuracy is reduced.
In order to prevent this, it is advantageous to improve the film circuit board into a flat film circuit board. In such a case, however, the following conditions must be met. First, the area just irradiated with exposure light during exposure of the peripheral area must be improved. In other words, because the evenness of the just-exposed area is not improved even if the vicinity of the irradiation area is improved greatly, the exposure light must be able to penetrate the pressing means. Secondly, the arch and a fold in the peripheral area of the TAB strip TP must be corrected while the TAB strip TP is being transported with a certain conventional speed. The device for exposure of the peripheral area is installed in a development apparatus which transports and develops the strip with a certain speed. When the transport of the strips is stopped temporarily or the transport speed is reduced to press the strip, therefore, different conditions for development must be changed. Furthermore, the throughput also decreases.
The primary object of the invention is to eliminate the above described disadvantages in the prior art in meeting the above described conditions in a device for exposure of a peripheral area of a film circuit board, and to be able to expose the peripheral area of the film with high precision even if the peripheral area of the film has an arch or a fold.
The object is achieved in accordance with the invention by providing a device for exposing the peripheral area of a film circuit board which includes a means for edge determination of the film circuit board including an optical detector having a light projection section for transmitting or projecting sensor light, and a light receiving part for receiving the sensor light, and a controller in electronic communication with the means for edge determination, the controller operating, based upon the output received from the means for edge determination, moves the area irradiated with the exposure light and the above described film circuit board in a relative manner. The controller also executes control such that the peripheral area of the film circuit board is irradiated with exposure light. A gas, for example, air, is discharged or blown into the area of the film circuit board which is subjected to peripheral area exposure and this area is pressed against a carrier with good evenness which is located on the bottom surface the film circuit board. Since the film circuit board is transported while being pressed by the gas against the above described carrier, the carrier is processed such that it acquires good evenness and the bottom surface of the film circuit board is prevented from being scratched during transport.
Preferably, the carrier against which the film is pressed is made of a material which transmits or reflects the sensor light so that the light receiving sensor of the means for edge determination receives the sensor light from the projection sensor.
Because a gas is blown on the film circuit board, an arch and a fold of the film circuit board in the area irradiated with exposure light is corrected without screening the exposure light while the film circuit board is transported.
Furthermore, pressing prevents the surface of the film circuit board from being scratched. By processing the carrier surface such that it acquires good evenness, scratching of the back of the strip can be prevented.
The invention is further described below using several embodiments shown in the drawings.